John 21:24
This is the disciple who testifies of these things and wrote these things, and we know that his testimony is true.
John 19:35
And he that saw it gives testimony, and his testimony is true, and he knows that he says the truth, that ye also might believe.
3 John 1:12
Everyone gives testimony of Demetrius, even the truth itself; and we also bear witness, and ye have known that our witness is true.
John 15:27
and ye also shall bear witness because ye have been with me from the beginning.
1 John 1:1-2
That which was from the beginning, which we have heard, which we have seen with our eyes, which we have looked upon, and our hands have handled, of the Word of life
1 John 5:6
This is Jesus, the Christ, who came by water and blood; not by water only, but by water and blood. And the Spirit is he that bears witness, because the Spirit is the truth.